# Full text of "Handbook Of Chemical Engineering - I"

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```MATERIAL HANDLING— TRANSPORTATION OF SOLIDS          85
the average cost of a 5-ton, medium-speed, crane of 25-ft. span taken as 1 are given in Table 6. This data provides sufficiently reliable values for comparing the cost of various sizes of cranes and for purposes of estimating the probable cost of the equipment, etc.
Base: 5-ton, medium-speed, crane of 25-ft. span = 1.
Depreciation of overhead electric cranes is customarily figured at 5 per cent of cost — a safe value — while ordinary repairs should not average more than 2 per cent. Interest on investment, insurance, taxes, etc., add another 8 per cent of the initial cost of the equipment per year, making the average burden 15 per cent. One man to run the crane with some occasional service from an assistant constitutes the necessary operating crew, the expense of which should not average per hour more than one and three-seventh times the hour-wage rate of the craneman. Oil, waste and incidental supplies, including the expense of an occasional careful overhauling and thorough cleaning of equipment, varies closely with the total power consumption of the crane and may be taken at a mean value of 0.15 ct. per total motor horsepower per hour. The average power requirements, including the power required to run the crane empty as well as under load is in kilowatts per hour taken as equal to half the total horsepower requirements of the crane expressed in horsepower per hour.
The total net cost of operating the crane for a period of a year should be the basis of estimating the net operating cost per hour or per ton handled, in order that the burden expense may be equitably apportioned. If this is not done, it is necessary to allot arbitrarily a certain proportion of the yearly burden to the operating expense for the period under consideration. The net cost of operating a standard overhead electric crane, expressed in the cost per ton handled and per hour of operation, follow as Formulas (6a) and (66) :
C/t = (P                                Formula (6a)          C/hr * C/t X Q"      Formula (6Z>)
Where,
P = Average power cost = consumption in kilowatts per hour times unit rate =
0.5 times total crane horsepower per hour times unit power rate, L = Labor charge per hour = 1.43 times hour-wage rate of craneman, E = Incidental expenses per hour = 0.15 times total crane horsepower per hour, T = Task duration (yearly) in hours,
B = Burden (yearly) = 0.15 times initial cost of equipment, Qf = Quantity of material handled in tons, and Q" = Quantity of material handled in tons per hour — bucket, or crane, with